Heretofore, there have been proposed various mechanisms for loading a cassette into a tape recorder/player. These mechanisms, however, have such a defect that they are subject to a considerably large load during loading and/or ejecting of the cassette, preventing smooth operation thereof. These cassette type tape recorders/players have a prominent advantage over other types of tape recorders/players in that they can be formed thin and be of small-size because the cassette used therewith is thin and small, but, on the other hand, these tape recorders/players are difficult to design in a reliable manner because of the requirement that the various movable mechanisms and components thereof, such as a cassette receiving frame, an ejecting mechanism associated with the cassette receiving frame and a head plate mechanism, be smoothly and easily actuated by a force applied by the insertion of a thin small cassette. In addition, these components and mechanisms are each provided with a resetting spring. A similar and even greater problem exists with regard to the ejection of the cassette because the ejecting operation is carried out by a depressing operation of a tiny push button. The known cassette loading mechanisms have a further disadvantage that the structures thereof have been bulky.